The invention particularly finds application in so-called structural engines, as used in agricultural tractors. Instead of being supported on resilient mounts on a vehicle body or chassis, a structural engine and its transmission train together form the unsprung mass or chassis of the vehicle. For this reason, the engine block needs to be designed to provide strength and rigidity.
The rear end of the block of a structural engine commonly has a flange that projects laterally and is used to support ancillary units, such as a fuel pump and a hydraulic pump to be driven by the crankshaft. The ancillary unit mates with the forward facing surface of the lateral flange and this surface must therefore be machined accurately after the engine block has been cast. In a structural engine, for additional strength, the block has laterally projecting ribs that are joined to the lateral flange on which the ancillary unit is mounted and these ribs interfere with the machining of the forward facing surface of the flange.
In order to enable an ancillary unit to be mounted on the lateral end flange of an engine without the need to machine the forward facing surface of the end flange, it has been proposed in EP-A-0.992.672 to mount an adapter on the rear end face of the lateral flange to overlie the aperture for the ancillary unit, the surface of the adapter plate facing the aperture being machined to mate with an ancillary unit disposed on the other side of the flange and secured to the adapter plate through the aperture in the lateral flange.
As a development of the adapter plate disclosed in EP-A-0.992.672, it has also previously been proposed to provide a drive adapter as shown in FIG. 1 of the accompanying drawings. The known adapter comprises a casing 12 for mounting on the end face of the lateral flange 10 to overlie the aperture, which casing 12 is sealed relative to the aperture by means of O-rings 28 and 30. The casing 12 has ears 14 for receiving bolts that secure the adapter to the end face of the engine. A drive shaft 16, which is journalled in the casing 12 by means of bearing shells 18, is formed at one end with a formation, such as a splined hole 22, for enabling the drive shaft 16 to be coupled to the input shaft of the ancillary unit. At its other end, the drive shaft 16 is provided with a cog 20 that meshes with the flywheel or another engine driven gear. The drive shaft 16 is formed with a double shoulder 24 and the cog 20 fits over a reduced diameter portion of the shaft 16. A retaining plate 26 screwed to the casing 12 abuts the shoulder 24 and the cog 20 to resist axial loads on the shaft 16 and holds the shaft 16 in the casing 12.
In the known drive adapter, the casing 12 is sealed relative to the engine flange 10 by means of two O-rings 28 and 30. Oil for lubricating the bearing shells 18 is supplied through a passage (not shown) lying between the two O-rings. If the O-ring 30 shown to the left in FIG. 1 should fail then an undesirable leak will occur. Replacement of the O-ring in the known drive adapter could only be carried out by first removing the adapter from the engine and this operation itself necessitates separating the engine from the transmission.
The present invention seeks to improve on the known drive adapter by allowing replacement of the O-ring without the need to remove the adapter from the engine flange.